1. FIELD:
The subject invention is in the field of springs, particularly springs involving relatively small deflections and high spring rates. Still more particularly it is in the field of springs used in the soles of footwear.
2. PRIOR ART:
There is profues prior art in this field exemplified by the following patents, selected from 49 patents found in a preliminary search of prior art related to the subject invention.
______________________________________ U.S. Pat. No.: 291,490 2,468,886 3,822,490 4,283,864 354,986 2,565,108 3,384,040 4,451,994 1,693,911 2,668,374 4,187,620 4,521,979 2,434,770 2,953,861 4,267,648 4,535,553 4,536,974 British: 565,723 ______________________________________
The basic problem addressed by the listed inventions is a combination of (1) reduction of the chances of the occurrence of foot damage and associated pains and injuries resulting from walking, running, jumping and the like and (2) corollary potential for improvement of the performance of the wearer of shoes having resilient soles in terms of increased stamina and/or improved athletic capabilities. NOTE: For purposes of this disclosure the term sole is construed to mean all or part of the elements of footwear supporting a wearer's foot. The longstanding need for a solution to this combination of problems continues in spite of the efforts made to solve them as evidenced by the profusion of prior art. Specifically, the need is for springs, and shoe soles with the springs incorporated into them, which provide specific levels of spring capability (energy absorption and release) for lower weight and smaller size than has yet been provided. This can be accomplished in large part by providing springs having essentially linear spring rates. Further, this accomplishment can be supplemented by providing a range of springs having a range of associated spring rates to suit a range of weights of users. This accomplishment is achievable only if the spring characteristics can be accurately predicted and produced. Also, it has been determined that prior art shoe sole springs are not adequately stable laterally, i.e. they deflect in directions essentially parallel to the sole of the shoe into which they are incorporated. Accordingly, the prime objective of the subject invention is the provision of springs which can be incorporated into the soles of footwear and provide improved ratios of energy storage and release capabilities of the soles to both weight and size of the soles. More specifically, it is an objective to provide springs having essentially linear spring rates. It is an objective that the springs have high efficiency and further it is an objective that the spring features readily enable provision of a range of springs having a range of spring rates related to the weights of the users of footwear incorporating the springs. It is a further objective that the spring rates be accurately predictable and producible. Another objective is that the springs be laterally stable, i.e. their deflection capability be restricted essentially to the direction normal to the soles of shoes into which the springs are incorporated. A further objective is that the springs concept enable relatively simple and economical manufacture of the resilient soles. Further objectives will become evident to those skilled in the art from understanding of this disclosure.